The invention relates to a method of building a composite using reinforcement cords and composites made using such method.
It is a continuing goal in the tire industry to reduce the cost of manufacturing tires without sacrificing tire properties. One way in which cost can be reduced is by reducing the handling cost involved in material preparation when strength and durability characteristics are not sacrificed, or when the material is used in a tire component where strength and durability properties need not be significant.
In the prior art, tire reinforcement cords are twisted; first the yarn (ply) used to make the cord, and then the cord itself, to increase the durability and fatigue resistance of the cord. The ply twisting and the cord twisting are both time and energy consuming operations, and handling costs are reduced by eliminating or reducing one or both of these expensive steps.
For several years, Goodyear has reduced the expense of reinforcement cords for certain tires by reducing the yarn twist while maintaining the conventional cord twist. For example, when a Z ply twist of 197 tpm (turns per meter) (5 tpi (turns per inch)) is used, an S cord twist of 334 to 472 tpm (8.5 to 12 tpi) is used. In theory, it is believed that yarn twists of 118 to 472 tpm (3 to 12 tpi) can be used as long as the twist multiplier (TM) is 10 or less and the yarn twist is maintained less than the cord twist. It has been found, however, that treated fabric and reinforced rubber composites made with such cords are difficult to process since the residual torque, caused by the unbalanced twist in the cords, causes the treated fabric, and sometimes the fabric reinforced composite, to roll up at the edges, and the cost savings obtained by the reduced twist in the ply (yarn) is partly or totally lost due to the increased handling cost of the fabric and the composite.
In certain tires, specifications call for reinforced components having cords with an S twist to alternate with cords having a Z twist in the reinforced structure. In the conception of the invention, the inventors have theorized that if reinforcement cords with a reduced yarn twist are alternated S and Z in a fabric, the torques applied to the treated fabric and a resulting fabric reinforced composite by the S and Z cords would neutralize each other and eliminate the handling problems, thereby reducing the cost of tires specifying S and Z reinforcement.